Feline tooth resorption

What it is

In tooth resorption, cells called odontoclasts destroy the cementum, dentine and finally the enamel of a permanent tooth. It was formerly called "feline odontoclastic resorptive lesion" or "neck lesion". The cause has not been established; dietary factors (such as excess vitamin D) and ageing have been studied without firm conclusions. The lesion usually starts on the root surface near the cementoenamel junction and progresses; when it reaches the crown, the pulp is exposed to the mouth and the tooth hurts. The American Veterinary Dental College classifies lesions by their radiographic appearance:

• Type 1: focal or multifocal radiolucency with otherwise normal root radiodensity and periodontal ligament space; associated with inflammation (periodontitis, gingivostomatitis).
• Type 2: the root loses its radiodensity and the periodontal space disappears, because the tooth fuses with the bone (ankylosis) and is gradually replaced by bone (replacement resorption).
• Type 3: combines features of both types in different roots of the same tooth.

The extent is also graded in stages 1 to 5, from minimal loss of cementum or enamel to loss of the crown with only root remnants under the gingiva.

Who it affects

Adult cats; it is very common and its prevalence increases with age. Several teeth can be affected in the same cat. The mandibular third premolars are the teeth most often affected, although any tooth can be involved.

Anatomy involved

• Teeth and alveoli: the lesion destroys the cementum and dentine of the root and crown; in type 2 the alveolar bone of the mandible or maxilla replaces the root.
• Gingiva: inflamed, proliferative gingival tissue often fills the crown defect at the neck of the tooth.
• Mandible and maxilla: intraoral radiographs show the relationship between the root, the periodontal ligament and the alveolar bone.

Clinical signs

Many cats show no obvious signs, because they hide pain. Some chew on one side, drop food, prefer soft food, drool, show jaw chattering or trembling when the tooth is touched, have halitosis or lose appetite. On examination a defect is seen at the neck of the tooth, often covered by reddened or hyperplastic gingiva.

Diagnosis

• Oral examination under anaesthesia: each tooth is checked with a dental probe or explorer; a crown or neck defect with hyperplastic gingiva is characteristic. Touching it with the probe can trigger a jaw-chattering reflex even under anaesthesia.
• Full-mouth intraoral dental radiographs: essential, because many lesions affect only the root and are invisible on examination; they allow the type to be classified and the treatment chosen.

Treatment

No treatment stops the resorption; restorations fail. Affected teeth with clinical signs or with the lesion exposed to the mouth are treated surgically:

• Types 1 and 3: complete extraction of the tooth, including all roots, usually by a surgical flap technique.
• Type 2: when there is no periodontitis, endodontic disease or stomatitis, crown amputation with intentional root retention may be performed, leaving the root remnant to continue resorbing and being replaced by bone.

Root-only lesions without signs or exposure can be monitored with periodic radiographs. After treatment cats usually eat better and become more active; annual dental examinations with radiographs are recommended.

Key studies

• FelineVMA guidelines (Lobprise et al., 2025): the current reference guideline on feline oral health. They cite published tooth resorption prevalences of 28.5% to 67%, consider full-mouth intraoral radiography essential, recommend complete extraction for type 1 and crown amputation for type 2, and reserve monitoring for root-only lesions with no crown extension and no pain on probing.
• Lommer and Verstraete (2000), a retrospective study of full-mouth radiographs in 265 cats. 60.8% had at least one resorptive lesion (567 teeth in total). Lesions were not associated with periapical lucencies, which supports crown amputation with root retention in selected cases. The cats were dental patients at a referral hospital.
• Eriksson et al. (2024), a diagnostic accuracy study in the cadavers of 144 unowned adult cats, which underwent oral examination, dental radiography and cone-beam computed tomography. Oral examination detected only 36% of lesions, radiography 78.9% and cone-beam CT 99.5%, with specificity close to 100% for all three. Estimated prevalence was 40% of cats and 6.1% of teeth.
• Vapalahti et al. (2024), a case-control study in Finland with 202 cats with tooth resorption and 742 controls, all examined under sedation. Risk increased with age (from 14.7% in the youngest group to 25.3% in the oldest) and with gingivitis or periodontitis accompanied by calculus (OR 2.49 and 3.70). Cornish Rex, European and Ragdoll cats were at higher risk, and the Exotic-Persian group at lower risk. The data come from an owner survey of veterinary diagnoses.
• Girard et al. (2010), 64 healthy cats fed dry food all their lives, with full dental radiographs and serum vitamin D (25-OH-D) measurement. Cats with more than 5 lesions had lower concentrations than cats without lesions, so the study does not support the idea that excess vitamin D causes resorption. It is a small sample from a single colony.